1. Field of the Invention
The present invention relates to a plasma deposition or etching method and various apparatus for depositing a thin film onto a substrate or for removal (etching) of a film from a substrate.
2. Description of Related Technology
Etching
Plasma etching involves using chemically active atoms or energetic ions to remove material from a substrate. It is a key technology in the fabrication of semiconductor integrated circuits. However, before the advent of microwave plasmas utilizing electron cyclotron resonance (ECR) it was becoming difficult for conventional plasma etching techniques to satisfy the requirements dictated by the increase in device packing density. Specifically, the requirement for fine pattern etching without undercutting (anisotropic etching) and the requirements for low damage and high selectivity could hardly be satisfied at the same time.
Deposition
Plasma Enhanced Chemical Vapor Deposition is a widely used technique to deposit materials on substrates in a host of applications. In normal CVD the chemical reaction is driven by the temperature of the substrate and for most reactions is high (&gt;800.degree. C). The high substrate temperature needed precludes use of this method in a number of applications particularly in microelectronics, displays and optical coatings. The role of the plasma is to dissociate and activate the chemical gas so that the substrate temperature can be reduced. The rate of dissociation, activation and ionization is proportional to the density of the plasma. It is therefore of importance to make the plasma as dense as possible.
Sputtering
Sputtering is also a widely used method for depositing materials onto substrates for a wide variety of applications such as the production of hard or decorative coatings and the coating of glass. In general, a plasma is produced at the sputter target material and the sputter target is biased to a negative voltage of around 700 V. Plasma ions, generally argon, impact the surface and sputter the material which then transports as neutral atoms to a substrate. Reactive gases can be introduced to chemically react with the sputtered atoms at the host substrate in a process called reactive sputter deposition. Rate is often important and it is therefore important to make the plasma as dense as possible. Ionization of reactive gases is also important and is helped by having plasma in the vicinity of the substrate material. Sputtering is also done by ions accelerated in an ion or plasma gun and then made to bombard the sputter target. In this case, a bias voltage on the target is not necessary. For sputtering insulating materials, RF voltage bias can be applied to the sputter target.
Existing Methods
There are presently two widely used methods for plasma deposition and etching, the parallel plate reactor and the ECR plasma deposition system.